Portable backup power supply



FIG. 1 is a perspective view of an portable backup power supply according to our new design;

FIG. 2 is a front elevational view of the portable backup power supply of FIG. 1;

FIG. 3 is a top plan view of the portable backup power supply of FIG. 1;

FIG. 4 is a bottom view of the portable backup power supply of FIG. 1;

FIG. 5 is a rear elevational view of the portable backup power supply of FIG. 1;

FIG. 6 is a left hand side elevational view of the portable backup power supply of FIG. 1; and,

FIG. 7 is a right hand side elevational view of the portable backup power supply of FIG. 1.

The broken lines which define the bounds of the claimed design form no part thereof. 

The ornamental design for a portable backup power supply, as shown and described. 